SU0013451 - Laserfiche WebLink

Home Browse Search

LARGE SANDHILL CRANES WINTERING IN CALIFORNIA 267 o ulation as Threatened under California's northern regions of the intensive study area,Chi- I I the P P State Endangered Species Act.The Pacific Flyway co, Afton,and the Butte Sink,are contiguous and Management Plan for the Central Val- are located in the eastern Sacramento Valley. ley Population of Greater Sandhill Cranes These three regions extend from the Sacramento i (U.S.F.W.S. 1983) recommended winter surveys River east to within l km of Highway 99. The to provide indices of the size of the population Chico region comprises S l0 km2 and extends and monitor winter distribution. This study was from the city of Chico south to Highway 162, conducted to accomplish these goals. The spe- while the Afton region includes 240 km' and i cific objectives of this paper are to: 1) present extends from Highway 162 south to the Colusa- recent estimates of the population's size, 2) de- Gridley Highway. The Butte Sink region com- lineate and identify important wintering sites, 3) prises 300 km2 and extends from the Colusa- describe winter movements, and 4) discuss the Gridley Highway south to near Highway 20 and status of the population. east to the vicinity of Gridley and the base of the Sutter Buttes. Rice culture, natural vegetation STUDY AREA (riparian woodlands,annual grasslands,and pas- California's Central Valley is approximately 640 tures), and orchards covered 38, 20, and 10%, km long and averages 65 km in width, encom- respectively, of the 1,055 km2 eastern Sacra- kml. Topography mento Valley (California Dep. Water Res., un- passing approximately 41,500 is generally flat and the valley is dissected by publ.). During winter, flooded ricelands, pas- numerous rivers and streams. Elevations on the tures, and areas of native and managed marshes, valley floor range from 14 m above mean sea covering approximately 20% of the Butte Sink level(M.S.L.)at Chico to 3-7 m below mean sea region (Heitmeyer et al., 1990), provided im- level on the S-SJ Delta. California white oakportant The two study regi habitat uareas.nting n the md-C'd-Central Val- (Quercus Iobata) woodlands, grasslands, wetlands present in the valley in the late 1800s ley, Thornton and the Cosumnes, are located on ` have been drastically reduced and altered by ag- the northeastern S-SJ Delta. The Thornton re- ricultural and urban development, flood control, gion comprises 240 km2 and extends from Wal- water diversion, and drainage projects (Holstein nut Grove and Thornton south to Highway 12, 1984, Katibah 1984, Gilmer et al. 1982). Ap- and from Grand Island east to Interstate 5. The P ,ro imately 11%of the riparian woodlands pres- Cosumnes region includes 90 km2 on the flood- it ent in the Central Valley in 1848 remained in plain of the Cosumnes River from Highway 9 1984 (Katibah 1984), and less than 6% of the south to the Mokelumne River, and from Inter- 16,000 km2 of wetlands present in 1850 re- state 5 east to the vicinity of Galt. On the S-SJ mained in 1980. Sixty-nine percent of the wet- Delta, the most important crops and land uses lands remaining in the early 1980s were in pri- were corn, pastures, and vineyards, which cov- 1 vate ownership (Gilmer et al. 1982). Heitmeyer ered 30, 15, and 12% of the region, respectively et al. (1990) described the wetland habitats in (California Dep. Water Res., unpubl.). Water- ; t the Central Valley. Agriculture is the primary fowl hunting areas on the S-SJ Delta were created b flooding harvested infields and pastures, land use, with orchards, cereal grains, and row y g gra P ! crops dominating. The climate consists of warm and made up approximately 3% of the region. i ryki dry summers (mean high and low temperatures To the south, the Modesto region, located in '. . in July are 35.7° and 16°C, respectively), and the northern San Joaquin Valley, includes 110 cool, wet winters (mean high and low tempera- km2 at the confluences of the Stanislaus, Tuol- ��j tures in January are 13.4°and 3.6'C, respective- umne, and San Joaquin rivers 16 km west of ISS 1 Seventy-five percent of the proximate) 33 � y). Y- Pe approximately Modesto. Dominant land uses m the Modesto cm average annual precipitation falls as rain from region were pastures(47°f%), row crops(16%), ce- I October through March(U.S. Dep.Comm. 1985). real grains and orchards (12% each) (California Periods of dense ground fog, lasting up to several Dep. of Water Res., unpubl.). Waterfowl hunting - weeks, are common during winter. I TYte study area included the entire Central Val- Less were not a prominent feature of this region. ■ Less intensive surveys were also conducted in ley,but intensive ground surveys were conducted ■ in eight geographic regions which encompassed the vicinity of Merced NWR and Pixley NWR approximately 1,500 km2 (Fig. 1). The three in the central and southern San Joaquin Valley. . l' L z VI-127 ate.-.